The present invention relates to a pressure-sensitive recording material including such a sheet excellent in the durability and definition of the recorded images transcribed on another sheet, which is produced by the process comprising the step of applying the microcapsules encapsulating minute particles of a pigment dispersed in a solution of an adhesive and optionally, an oil-soluble coloured dyestuff dissolved in a solvent onto a supporting material such as sheet, and a process for producing the same.
Hitherto, as the most generalized pressure-sensitive recording material including a sheet, there has been known the so-called "carbonless recording paper" which utilizes the coloured product formed by the reaction between a colourless dyestuff and a colour developer.
Such carbonless paper for pressure-sensitive recording is constituted by the combination of a sheet of paper (a supporting material) having its undersurface of which has been coated with the microcapsules containing a solution of the colourless dyestuff in a solvent (the thus prepared sheet of paper being referred to as CB sheet) and another sheet of paper having its upper surface of which has been coated with the colour developer for forming the coloured product (the thus prepared sheet of paper being referred to as CF sheet).
Furthermore, in the case where a plurality of recorded copies are requested in the above-mentioned system, such pressure-sensitive recording paper is constituted by further combining a sheet of paper having its upper surface of which has been coated with the colour-developer and its undersurface of which has been coated with the microcapsules containing a solution of the colourless dyestuff in a solvent (the thus prepared sheet of paper being referred to as CFB sheet) with the above-mentioned two kinds of sheets, i.e., CB sheet and CF sheet (Japanese Patent Publication No. 49-2124 (1974) and U.S. Pat. No. 3,836,383).
The pressure-sensitive recording paper according to the above-mentioned system is excellent in its performances in copying and recording and is broadly utilized for those purposes.
However, on the other hand, its construction is complicated due to the use of many kinds of chemicals, and because of the use of coloured product formed by the utilization of chemical reaction, the sheet of paper is apt to be deteriorated by contact with water and chemicals.
Accordingly, much attention is necessary for the preservation of the pressure-sensitive recording material and/or the maintenance of the developed and recorded images on another sheet material. If anything should happen, the important recorded image would disappear from the sheet of paper resulting in incapability of playing the role as the material for recording. The same phenomenon of the disappearance of the coloured image is also caused by exposure to light and accordingly, the handling of such a kind of pressure-sensitive recording material including a sheet becomes complicated furthermore.
As another kind of pressure-sensitive recording material including a sheet, the so-called "carbon paper" has been known. Such a kind of pressure-sensitive recording material has a pigment weakly held on the undersurface of a supporting material (a sheet of paper) by a wax, and the image is transcribed on another sheet of paper (underlaid sheet of paper) a face of which has not been coated with specified chemical with a pressure applied on the uppersurface of the supporting material.
Such a pressure-sensitive recording material including a sheet has a merit of possibly forming the images on an ordinary sheet of paper (namely, a sheet of paper a face of which has not been coated with specified chemical. However, on the other hand, because of the very weak holding of the pigment on the surface of the sheet of paper (the supporting material), stains are apt to be caused during the preservation and in the case of handling thereof. In addition, since the pigment is apt to adhere to the hands and clothes of the persons handling the material including a sheet, an excessive attention should be taken in the handling and the preservation of the materials including a sheet before and after the use thereof. Furthermore, the transcribed images are only weakly held on the surface of another sheet, and the images stain the circumference thereof by friction of the transcribed surface not only to deteriorate the quality of the thus transcribed images but also to cause the misreading thereof.
In addition, in the case of using the pressure-sensitive recording material disclosed in Japanese Patent Application Laid-Open No. 57-98390, which is produced by applying the microcapsules containing a solution of an oil-soluble coloured dyestuff on the undersurface of the supporting material, it is not possible to obtain the images which are stable for a long period because of the poor light-stability of the image.
As has been described above, the pressure-sensitive recording material including a sheet produced by the conventional techniques does not exhibit sufficient performances concerning the durability and definition of the recorded images, and in addition, the conventional pressure-sensitive recording material have a problem also of instability before colour-development. For instance, in the case of "carbonless recording paper", an entire colour-development is caused on the whole surface of the paper by exposure to light, and in the case of carbon paper, the paper is stained by heat. Accordingly, much attention has been necessary in the handling of the recording paper before colour development and in the preservation and handling of another paper holding the recorded images.
Namely, strongly demanded is the offer of the pressure-sensitive recording material including such a sheet, which can be easily preserved and handled and gives a stabilized, recorded images, however, such an object has not been attained.
In addition, recently, it has become regarded as important to read the recorded images by using an optical instrument, thereby improving the efficiency of information-treatment and accordingly, it has been strongly demanded to raise the durability and preservability of the recorded images themselves as well as the accuracy in reading the recorded images by such an instrument.
The first object of the present invention is to provide the pressure-sensitive recording material including such a sheet excellent in the durability and the preservability of the recorded images transcribed on another sheet and high in accuracy in reading the recorded images by the optical instrument.
The second object of the present invention is to provide the process for producing the above-mentioned pressure-sensitive recording material including such a sheet.
As a result of the present inventors' studies for solving the above-mentioned problems, the present inventors have found that the pressure-sensitive recording material including such a sheet excellent in the durability and preservability of the recorded images and high in the accuracy in reading by the optical instrument and can be handled easily without any complexity is available by the use of the sheet of paper coated with the microcapsules containing the minute particles of a pigment dispersed in a solution of an adhesive dissolved in a hydrophobic solvent as the core material thereof or the microcapsules containing the microcapsules of the pigment dispersed in a solution of both the adhesive and an oil-soluble coloured dyestuff dissolved in a hydrophobic solvent as the core material, and on the basis of the finding the present invention has been attained.